The present invention relates to a method and installation for the continuous production of whipped ice.
A liquid ice-making machine and method, as seen in U.S. Pat. No. 5,383,342, shows that a solution, passing through at least one tubular element, is cooled by direct contact with a cooling surface (ice crystal nuclei moved from said inside surface throughout the entire volume of said tubular element). An ice separator continuously discharges ice crystals separated from a mixture of concentrated solution and ice crystals from the tubular element.
However, the method according to the above patent, can be disadvantageous if clogging along the entire tubular element volume arises. Ice crystals are removed from a cooling surface by teflon cutting blades. The cutting blades revolve on their shaft at a high revolution rate per minute causing a mass of solution to be forced from the shaft in all directions to the cooling surface. The ice crystals, in turn, speed to the axis of the tubular element, due to the existing difference between densities of ice and solution. New portions of ice continuously press and envelop the revolving shaft. At the same time, the flow rate of ice withdrawing from the volume of the tubular element is dependent on only one factor, i.e., the flow rate of the solution. In the case of a vertical evaporator, there is an additional factor--gravitational (buoyancy) force. If the flow rate of the ice mass leaving the evaporator is low, then the above mentioned clogging process is dramatically accelerated. This clogging causes a severe increase of the shaft motor's torque demands (measured as current) and the liquid ice production process is stopped. Increasing the flow rate of the solution causes insufficient sub-cooling of the solution in the volume of the evaporator, thereby causing the liquid ice production to be decreased.
A further serious disadvantage of the above mentioned method is the fact that in order to scrape away ice nuclei from an insufficient polished cooling surface, the strength of wipers must be strong enough to survive full contact between the blades and the cooling surface along the evaporator's axis. Because the blades are made from teflon or similar plastics, which are very soft materials, the thickness of crystal "wall" ice, which is frozen to the cooling surface, is not scraped away after every new revolution of the blades. This causes a sharp decrease of heat transfer between the solution and the refrigerant. Besides the increased insulation, the pressing of the blades against a thickening ice layer is quite deleterious. As a result, the shaft motor current is increased and the liquid ice process is stopped. The blades used for ice nuclei cutting and moving from the cooling surface are blunted.